The invention relates to a method of detecting at least one predetermined shift position of a vehicle transmission among a plurality of different shift positions corresponding to different rotary transfer ratios between an input shaft and an output shaft. It further relates to a control device, to a vehicle transmission, as well as the use of the method, the use of the control device, and the use of the vehicle transmission. In addition, the invention also relates to a method of detecting a position change in relation to a reference position of a vehicle transmission.
A transmission in the present context means a device that can be shifted into different states, by an either stepwise or continuous variation, to generate different rotary transfer ratios between two shafts. The transmission is configured as a gear-changing transmission or a cone-pulley transmission, or other appropriate mechanism. The shift processes of the transmission can be controlled automatically or manually, or in a partially automatic mode, or in an automated mode that permits manual intervention by the driver. A transmission in the sense of the present invention can be configured so that shifts from one gear ratio to another cause an interruption in vehicle traction, or it can be configured to perform shifts without interrupting traction.
With preference, the transmission is configured as an automatic transmission which, in the context of the present invention, means a transmission that shifts without interrupting traction. With special preference, however, the transmission is configured as an automated shift transmission, a term which is used in particular for a transmission in which the control of the shift process is automated but causes an interruption in vehicle traction.
Transmissions as well as operating methods for transmissions belong to the known state of the art.
In a manual transmission, the gear shifts are performed manually by the driver. In principle, the driver is free to shift arbitrarily from any gear into any other gear. The driver chooses when to shift gears and which gear to shift into, based on certain criteria. The driver will decide to shift gears particularly in response to the sound of the engine and depending on which of the gears is currently engaged.
Errors in recognizing which gear is currently engaged, errors of shifting into an other than the intended gear, judgment errors about the need to shift gears, or other mistakes can cause damage to a transmission or can stall the engine of a vehicle. This kind of situation can occur, for example, in a vehicle coasting downhill with the transmission set to the neutral position, if the driver""s foot is on the gas pedal so that the engine runs at a high rpm rate but the driver erroneously believes the transmission to be in first gear and therefore shifts into second gear.
Also known are automated shift transmissions in which the shifts are actuated by two electric motors. The electric motors apply a force to a shifter finger. The shifter finger moves in a pattern that consists of a selector track (also called neutral track) and shift tracks branching off from the selector track. The first of the electric motors moves the shifter finger in the direction of the shift tracks which terminate at the different gear positions, while the second of the electric motors moves the shifter finger in the direction of the selector track where the transmission is in the neutral state.
The shifter finger position is monitored by displacement sensors which are arranged at the electric motors and work according to an incremental detection principle.
The shifter finger is controlled by the electric motors dependent on the position values generated by the incremental sensors.
Automated shift transmissions of the foregoing description provide a satisfactory level of shifting and driving comfort and an economical way of operating a vehicle.
However, there have been incidents where gear shifts where performed incorrectly by transmissions of this type. Incorrect gear shifts are detrimental to the driving comfort in a vehicle with an automated shift transmission and will shorten the life of the transmission.
The present invention therefore has the objective of providing a method of operating a vehicle transmission, as well as a transmission capable of performing the method, with an at least reduced incidence of incorrect gear shifts, a longer operating life, and an improved level of comfort for the driver and passengers of a vehicle that is equipped with the inventive transmission. In particular, the invention has the objective of providing a method of operating a transmission, as well as a transmission capable of performing the method, wherein the current shift position or shift movements from one position to another can be detected and evaluated more accurately and reliably and wherein detection errors can be corrected, so that detected positions or shift movements reflect the actual positions or movements of the transmission.
To meet the objective stated above, the invention proposes a method of detecting at least one predetermined gear-shift position of a transmission that has a plurality of different operating states corresponding to different rotary transfer ratios between an input shaft and an output shaft of a vehicle transmission. A transmission that is operable by the inventive method has a shift pattern with a selector track and shift tracks. A first shifter element, in particular a shifter finger, is movable within the shift pattern. The transmission also includes a second shifter element, in particular a shifter shaft or a shift rod. The transmission is further equipped with an actuator device running under the control of an electrical control device to actuate at least one of the first and second shifter elements. At least one position-sensor device is provided in the transmission to determine the position of a movable element of the transmission.
The method according to the invention has the following steps:
a) When a set of predetermined conditions are present, an actuating force is applied by the actuator device to at least one of the shifter elements in accordance with a predetermined characteristic.
b) At least one characteristic electrical variable of the actuator device and/or the control device, particularly an electric current, is monitored as a function of time.
c) The profile of the electrical variable as a function of time is evaluated according to a predetermined evaluation characteristic to determine a shift position that the transmission is set at. This determination is based on a functional dependency between the time profile of the characteristic electrical variable and the shift position.
The shift positions to be determined by the inventive method include in particular at least one end position of a shift-track and/or at least one specific position in the selector track and/or any position in the selector track.
The second shifter element, which consists of a shifter shaft, a shift rod, a shift fork, or a similar element, is connected to the first shifter element.
The arrangement of a selector track and shift tracks, as well as the first and second shifter elements, are part of a gear-shifting mechanism.
At least one movable element of the gear-shifting mechanism, such as the first or second shifter element, can be subjected to actuating forces under the control of an actuator device, causing the element to move, at least to the extent that the movement is not prevented by other factors or elements of the mechanism, such as end stops.
An actuator device in the sense of the present invention is a device that can convert one form of energy into another, generating an output that actuates the shift mechanism or at least one of the movable elements of the shift mechanism. In particular, the actuator device has at least one electric motor that converts electrical energy into mechanical motion. With preference, the actuator device has two electric motors. The first motor, referred to as selector motor, can exert on the first shifter element a force in the direction of the selector track. The second motor, referred to as shifter motor, can exert on the first shifter element a force in the direction of the shift tracks.
A shift track in the sense of the invention can mean a physically existing shift track or a virtual shift track containing a position of the first shifter element where a predetermined gear or a predetermined rotary transfer ratio of the transmission is engaged, or it can mean a pair of shift tracks branching off from a given point of the selector track.
A virtual track means a concept where the shifter element can move only along certain track-like paths, constrained by the nature of control signals generated by the actuator device or the control device.
The actuator device is controlled by a control device.
A control device in the sense of the invention means in particular a device that supplies control signals and/or energy to the actuator device in accordance with a predetermined characteristic. In particular according to the inventive concept, the nature, duration, timing, direction, orientation, and force of the action exerted on the shift mechanism by the actuator device depends on the signals and/or on the flow of energy transmitted from the control device to the actuator device.
The invention provides in particular that the control device supplies the actuator device with current, i.e., with electrical energy, according to a predetermined characteristic.
A control device in the sense of the invention can be designed to provide energy and/or to control either the actuator device alone or at least one other device in addition to the actuator device, for example a clutch. Under a preferred concept of the present invention, the control device controls the actuator device through one or more voltage signals which may be of a set magnitude or variable according to a predetermined characteristic.
According to the invention, the transmission is equipped with a position sensor device that serves to detect shift positions by sensing the positions of components that are moved in the process of shifting.
A position sensor device in the present context means a device by which a position or a change of position can be detected in absolute or relative terms. In particular, the position sensor device can consist of a device that measures the length of a linear displacement or the angle of a rotary displacement. In particular, the position sensor device is configured to perform either an absolute measurement or an incremental measurement.
According to the invention, the actuator device will in the presence of certain conditions exert a force on at least one of the shifter elements in accordance with a predetermined characteristic, while during the actuation at least one characteristic electrical variable of the control device and/or the actuator device is detected and/or monitored as a function of time.
A characteristic electrical variable in the sense of the present invention is in particular a voltage or a current.
With preference, the characteristic electrical variable to detect or monitor is the total amount of current consumed and/or generated by the control device and/or the current consumed by the selector motor and/or the current consumed by the shifter motor and/or the current consumed by the actuating device. In particular, the process is voltage-controlled, where voltage signals are given according to a predetermined characteristic, and the currents flowing as a result of the voltages are monitored or detected.
Instead of monitoring a current, it is also possible within the scope of the invention to monitor another characteristic electrical variable. To represent the invention in simple terms, the example of a voltage controlled method is explained, in which a predetermined current is monitored or detected. However, the invention also includes concepts where another first characteristic electrical variable is used instead of a current, or another second characteristic electrical variable is used instead of a voltage.
According to the invention, the characteristic electrical variable, meaning the current in the case of the representative example, is evaluated as a function of time according to a predetermined evaluation characteristic in order to determine at least one of the shift positions of the transmission.
The predetermined shift positions that can be detected by one of the embodiments of the inventive method are in particular one or more of the shift-track end positions and/or the neutral position and/or any position where the first shifter element is located in the selector track.
The invention provides in particular that the evaluation of the current as a function of time will indicate when the first shifter element is positioned at a dead end, detents, specific locations within a track, or it will indicate in which track the shifter element is currently positioned.
The invention will be explained in further detail through the example of a transmission with a shifter finger, where the latter is representative of any kind of first shifter element.
In the present context, if a first shifter element or shifter finger is said to run against a stop, dead end, or boundary, the latter terms are understood to mean either an actual physical barrier or the occurrence of an effect that is comparable to a physical barrier. An effect comparable to an actual physical barrier means in particular that another element that is coupled to the movable element is running into a stop or is otherwise constrained from continuing its movement. A constraint that prevents a continued movement can be realized in particular by a preset limit in the control device or the actuator device. For example, an electric motor can be controlled so that it is switched off when reaching a predetermined amount of displacement in a given direction under a given set of conditions.
In the present context, if a movable element such as the first element or shifter finger is said to have reached an indent in a surface profile, or a detent, this means that the element is engaged in an actual physical detent or an analogous position-defining feature, or that another element that is coupled to the first element has a detent feature that is in an engaged position.
The invention has the advantage that predetermined positions of the transmission can be safely recognized even in case of a failure of the position sensor device, so that incorrect gear shifts are avoided. For example, the invention provides the possibility of detecting end stops of the transmission, the release of a blocked synchronizer, a detent position for the neutral state, or bias-free, settled positions of the transmission. The invention further provides the possibility that the position sensor device will adapt itself to these positions.
As a preferred concept, a method according to the invention can be used as an emergency mode that is used under a predetermined set of conditions. In particular, the emergency mode is started if the position sensor device has been found to produce faulty information or if it has failed completely, or produces signals that are contradicted by other factors.
In accordance with a particularly preferred embodiment of the invention, the electric current that is being monitored depends on the activities of the selector motor and/or the shifter motor in accordance with a predetermined characteristic. In particular, the electric current is stronger at times when the selector- and/or shifter motor is running. When the selector- and/or shifter motor consumes an increasing amount of power, the monitored electric current will likewise show an increase.
The invention provides in particular, that starting and braking currents are taken into account in the evaluation in accordance with a predetermined characteristic.
According to a particularly preferred embodiment of the invention, the monitored electric current depends in a predetermined characteristic manner on the travel path of the shifter finger and/or on the force that is exerted on the shifter finger by the actuator device.
Preferred is a concept where the electric current represents a combined characteristic effect of the activities of the selector- and/or shifter motor, the travel path of the shifter finger and/or the force acting on the shifter finger.
In particular, the invention provides that variable amounts of resistance opposing a movement of the shifter finger will have an influence on the electric current. In particular, by monitoring the current as a function of time, it is possible to determine whether the shifter finger is being pushed against an end stop and/or is positioned at an end stop and/or is running through a detent position and/or is located at a detent position and/or whether a movement of the shifter finger in a shift track has arrived at the selector track, or other information about the movement and/or position of the shifter finger. As a particularly preferred concept of the invention, detented positions of the shifter finger are associated with predetermined positions of the transmission, particularly the neutral state and/or a bias-free position in which a gear is engaged and/or at least one position within the selector track where a shift track branches off, or other characteristic positions of the transmission.
According to a particularly preferred embodiment of the invention, the current-monitoring function is performed on the total current of the control device and/or a current inside the shifter motor and/or the power current supplied to the shifter motor and or a current inside the selector motor and/or the power current supplied to the selector motor.
A highly preferred embodiment of the inventive method provides that the total current of the control device is monitored, but that the control device supplies current only to the actuator device alone and/or only to the shifter motor alone and/or only to the selector motor alone during the time period that is being monitored or evaluated.
Preferably, the current supplied to other consumer devices in the vehicle is measured in accordance with a predetermined characteristic and taken into account in the evaluation of the overall current balance.
As a preferred concept, the current as a function of time is used under certain conditions to detect when the shifter finger has reached the end point of a lateral constraint, for example when the shifter finger moves out of a shift track into the selector track. To make this detection possible, the shifter motor and the selector motor are both under power during the movement in the shift track, but as long as the shifter finger is prevented from moving in the selector direction, the selector motor is stalled and its current flow is therefore increased. As soon as the shifter finger has reached the selector track and is thus free to move in the selector direction, the current decreases. The decrease in the total current can serve as an indication that the shifter finger has reached the selector track.
According to a particularly preferred embodiment of the invention, the shifter motor is switched off or, in more general terms, the actuation in the shift direction is terminated after detecting that the shifter finger has reached the selector track.
Also among the preferred concepts, the actuation in the shift direction may be continued for a predetermined time period or a predetermined distance after the shifter finger has reached the selector track.
With particular preference, the switch-off point in the shift direction is adapted to the geometry of the selecting/shifting track pattern as well as to the geometry of the shifter finger. With special preference, after reaching the selector track, the shifter finger is brought into a position in which it can move in the selector track with a minimal amount of friction and/or without touching the lateral boundaries of the selector track.
According to a particularly preferred embodiment of the invention, after detecting that the shifter finger has reached the selector track, it is moved to a predetermined position in the selector direction. According to the invention, the predetermined position is a boundary of the selector track, in particular one of the end barriers limiting the selector track in the lengthwise direction.
The move to an end barrier of the selector track can occur immediately following the detection that the shifter finger has reached the selector track. Also among preferred concepts, the move to an end barrier of the selector track is performed independently of whether or not the arrival of the shifter finger at the selector track has been detected. As a particularly preferred concept of the invention, the move to the end barrier of the selector track serves to make an adjustment to the position sensor device in the selector direction. This procedure may be used, e.g., in a case where the position-sensor device for the shift direction is working correctly, but the detection in the selector direction is incorrect or has failed.
In accordance with the invention, the current of the selector motor or the total current of the actuator device is monitored while an actuator force is applied in the selector direction.
With preference, the selector motor is switched off after an end barrier in the selector direction has been reached. Also as a preferred possibility, the selector motor is reversed to run in the opposite direction after reaching an end barrier of the selector track.
Under another preferred concept, the movement of the shifter finger in at least one position is subjected to a local increase or decrease in the opposing force in at least one of the tracks. Under certain conditions, the local variation in the opposing force can manifest itself by an increase or decrease in the actuator current, so that the respective position can be detected by monitoring and evaluating the current.
A local variation in the opposing force can be effected in particular by detents at intermediate positions between the end stops of a track. More specifically, a component coupled to the shifter finger can be equipped with a detent or can be moved into a detented position.
As a practical embodiment of the preceding concept, a second shifter element, in particular a shifter shaft or shifting rod may have a surface profile with depressed and/or raised surface portions. A feeler contact element biased by a spring force follows the profile contour or exerts a force against the contour as the second shifter element moves in relation to the contact feeler element. This creates a variable force opposing or assisting the movement of the second shifter element, dependent on the location where the contact feeler element is positioned on the profile, and also dependent on the direction of movement of the second shifter element. For example, a profile depression is arranged in at least one fully engaged and bias-free gear position and/or in the neutral position and/or at predetermined positions of the selector track where at least one shift track branches off.
Following is an example of how a detent arrangement affects the actuator current of a shifter shaft that performs gear shifts through angular as well as axial movements. A single profile depression can be used to detect a position relative to both the shift direction and the selector direction. For example, the profile depression can be arranged at a specific point on the shifter shaft so that the contact feeler element engages the low point of the depression when the shifter finger is at an intersection between the selector track and a shift track.
The foregoing example is used only to illustrate special possibilities of the invention without limiting the scope of the invention in any way. A device where the resistance to the movement of a shifter element is used may also be configured in other ways. Furthermore the location of the movement-opposing or -assisting feature can also be arranged at other essentially arbitrary locations of the selecting/shifting track arrangement. Also, a substantially arbitrary number of different movement-opposing or -assisting features can be employed in an arrangement according to the invention.
As the shifter shaft is moved axially or rotated about its longitudinal axis in the process of selecting and shifting, the contact feeler element will in certain phases move towards a profile depression.
When the selector- or shifter motor is started up, an initial surge in the motor current can be detected, manifesting itself as a peak in the time profile of the current. Subsequently, the current will settle and stay at an essentially constant level until the contact feeler element reaches the profile depression, unless there are other factors influencing the current. Examples of such other influence factors include for example stall conditions where the shifter finger is acted on by a motor, but is constrained by a track boundary.
When the contact feeler element enters the profile depression, in this case a bowl-shaped formation, the spring-biased contact feeler element follows the down slope of the bowl. At first, the contact feeler element moves closer to the central axis of the shifter shaft. After passing through the bottom of the bowl, the contact feeler element (which stays in place while the shifter shaft moves) is pushed back again against the spring force. The interactive force between the contact feeler element and the profile surface is perpendicular to the profile surface at the contact point. Thus, there is a force component assisting the movement in a first phase where the contact feeler element moves towards the bottom of the bowl and opposing the movement in a second phase where the contact feeler element moves away from the bottom of the bowl. Corresponding to the amount of the total force required to maintain the movement, the motor current decreases in the first phase and increases again in the second phase. Thus, a local dip followed by a rise occurs in the profile of the actuator current. The low point of the current can be used to detect when the contact feeler element is at the detent or low point of the bowl-shaped depression. As the detent depression corresponds to a certain position of the shifter finger within the shifting/selecting track pattern, it is therefore possible to detect a position of the shifter finger based on the actuator current.
The foregoing concept can be used to detect for example when a gear is settled into an engaged position, or when the transmission is in the neutral position.
According to a particularly preferred embodiment of the invention, the foregoing concept is used in a such a way that there is a change in the force that opposes the movement of the shifter finger in at least one place between the end stops of a track, and the current profile and/or the change in the opposing force is used to identify which track the shifter finger is moving in. As a preferred possibility, when the shifter finger is actuated in the shifting direction, the arrival at the selector track can be detected from the actuator current. Specifically, a depression in the surface profile would be arranged at the intersection of a shifting track with the selector track. The respective shifting track will preferably have additional profile depressions, which can be detected from the variations in the actuator current as the shifter finger moves along the shifting track. Based on the pattern of depressions detected, it will be possible to detect the position of the selector track.
The foregoing concept of the invention is advantageous insofar as it allows the arrival at the selector track to be detected by actuating the shifter finger in the shifting direction only.
According to a particularly preferred embodiment of the invention, different tracks, and especially different shifting tracks, can be identified or distinguished from each other by monitoring and evaluating the actuator current.
Under the invention, it is in particular envisaged that each shifting track be distinguished by a characteristic number of profile depressions and/or profile peaks or detents. As the shifter finger moves through the shifting track, the profile depressions manifest themselves through local decreases followed by increases in the time profile of the current. Based on the number of profile depressions detected in this manner when moving through a shifting track, the respective shifting track can be positively identified and distinguished from other shifting tracks without the need for measuring signals of a displacement sensor.
The invention proposes the concept of detecting local or transient changes in the force opposing the movement of the shifter finger through the detection of local or transient extremes in the current.
In particular, such extremes include maxima and minima.
In particular, an increase followed by a decrease in the opposing force, as would occur at a profile peak, manifests itself as a local or transient peak followed by a dip in the actuator current. A decrease followed by an increase in the opposing force, as would occur at a profile depression, manifests itself as a local or transient dip followed by a peak of the actuator current.
In accordance with a particularly preferred embodiment of a method according to the invention, certain gear positions are detected according to a predetermined characteristic relationship, particularly as part of an emergency procedure. Particularly preferred is a concept where the transmission does not shift through all of the gears when performing the emergency procedure.
In particular, the invention proposes the concept for an emergency procedure to shift into gear positions in shift tracks that are distinguished by an end stop, detent, or other movement-resisting feature in the selector track at the point where the respective shift track branches off from the selector track.
A typical case in point is the double-H shift pattern, i.e., a shifting/selecting track arrangement with three selector track positions where shift tracks take off from the selector track, so that the transmission can be shifted into a total of six different gears. Under an emergency procedure as described above, the transmission would move into the shifting tracks that branch off from the end point of the selector track. Typically, this means shifting into first, second, fifth and reverse gears. It is particularly preferred if the transmission also finds and positively identifies the neutral position during this emergency procedure. In a particularly preferred embodiment for a shift pattern where fifth and reverse gears branch off at essentially the same selector position, the transmission will search for neutral, first and/or second, and reverse gears.
A four-track pattern is defined as a shifting/selecting track pattern where reverse, first, third and fifth gears lie in parallel shift tracks in the upper half of the pattern, and where second and fourth gears lie opposite first and third, respectively, in the lower half of the pattern.
Preferably, a detent or resistance barrier is arranged in the selector track between the branch-off point for first/second and the branch-off point for reverse gear.
In the search procedure, the shifter finger is moved towards this resistance barrier with a limited actuator force, so that the barrier, e.g., in the form of a profile peak, cannot be overrun without increasing the actuator force. This resistance barrier, which can also have the form of a profile depression, may likewise be used to find and move into the first and second gear positions under the emergency procedure.
As a preferred feature for an emergency procedure, after the shifter finger has reached an end of the selector track and is about to move from there into a shift track, the shifter finger is subjected to a continuing but preferably small force in the selector direction towards the end stop, to ensure that the shifter finger finds its way into the shift track.
In accordance with a particularly preferred embodiment of the invention, when searching for a predetermined gear position and before the shifter finger has entered the respective shift track, an appropriate step is taken to confirm that the shifter finger is in the correct selector position from which the targeted shift track branches off. This confirmation can be achieved, e.g., by taking the direction of travel into account in which the shifter finger was moving prior to reaching the branch point on the selector track.
For example, in a double-H shift pattern where the shifter finger has reached an end stop of the selector track while traveling with a first sense of direction, it can be confirmed that the end stop for that traveling direction belongs to the branch point for first/second gears. If the shifter finger has been moving in the opposite direction, it can be confirmed that the end stop for that traveling direction belongs to the branch point for reverse/fifth gears.
While the transmission searches for the different gear positions, the current is monitored, so that the end stops, detents, or other barrier features can be detected from the behavior of the current. The movement of the shifter finger can be directed dependent on the behavior of the actuator current, so that the shifter finger is moved in a shift-track direction when the correct position has been reached.
In accordance with a particularly preferred embodiment, the inventive concepts are used in a phase of gear engagement, particularly under an emergency procedure, to detect the point of synchronization and/or the unlocking of the synchronization and/or the arrival at the end position of the shift track, and or the unbiased, engaged gear position.
The point of synchronization in the present context means the position at which the gears of a particular gear level are about to enter into meshing engagement. At this point, it will be necessary in certain situations for one of the gears to turn by a small amount in relation to the other before the tooth profiles can mesh with each other.
A completed synchronization or unlocked condition in the present context means a state where the gears of the ratio level to be engaged are in a position where the tooth profiles can move into engagement without the lateral tooth flanks blocking each other, which would constitute a kind of lock.
The invention proposes the concept of detecting one or more of the aforementioned positions or events on the basis of the actuator current.
For example, a point of synchronization can be detected by the fact that gears whose lateral flanks have come into mutual contact can under certain conditions at least temporarily prevent the gears from meshing with each other, so that further movement is blocked at least until the blockage is released. This locked condition causes a momentary increase in actuator current. When the current returns to a lower level, this indicates that the blocked condition has ended.
When a renewed increase in actuator current is detected after a predetermined time interval, this can be used as an indication that the shifter finger has reached the end of the shifting track.
Preferably, the actuation of the first shifter element in the shifting direction for shifting into first gear is terminated when the end of the shifting track has been detected.
According to a particularly preferred embodiment of the invention, the actuation in the shifting direction is continued for a predetermined time period after a resistance barrier has been detected in the shifting track. This has the purpose of distinguishing temporary barriers such as a blocked synchronizer process from permanent barriers such as the end of the shifting track. This distinction is particularly important if at the time of putting the transmission in gear, the tooth profiles happen to be mutually positioned so that their lateral tooth flanks are not interfering with each other, in which case no blockage occurs.
According to a particularly preferred embodiment of the invention, a shake-down phase is performed when the end stop of a shifting track has been detected in the course of shifting the transmission into gear.
A shake-down phase in the present context means a pulsating actuation of a movable element of the transmission. This can be achieved by driving the selector- and or shifter motor with voltage pulses of alternating polarity for a predetermined amount of time. The alternating pulses are for example in a range between 0.3 and 5 volts. Preferred are pulses between 0.3 and 3 volt, with special preference for pulses between 0.5 and 2 volt.
The shake-down causes the shifter finger and/or a component coupled to the latter to settle into an unbiased (force-free) equilibrium position.
Subsequently, the actuation of the shifter finger is terminated after a predetermined time period has elapsed.
As a preferred concept of the invention, after the unbiased position has been found, a plausibility test is performed whether the actually engaged gear is the one that was intended. This can be established by checking whether the ratio between the engine rpm rate and a wheel rpm rate correlates correctly with the intended transmission ratio.
According to a particularly preferred embodiment, a shake-down phase is performed when the transmission is put into neutral, so that the shifter finger and/or transmission components coupled to the latter will settle into an unbiased condition.
A process according to the inventive method is started with preference after detecting certain kinds of faults of the sensor device and/or the actuator device and/or the control device. A fault in the present context means in particular any impairment of functionality. A fault in the present context can also mean a loss of confidence in the position values determined by the position sensor device. The loss of confidence can occur, for example, if blockages of shift movements occur at unexpected times or in unexpected positions.
According to a particularly preferred embodiment of the invention, a determination of a position through one of the procedures of the inventive method may under certain conditions be performed as a redundant measure, for the purpose of adapting the position sensor device or its output values to changes in the system.
According to a particularly preferred embodiment of the invention, a redundant position information is used to control the transmission only if the values generated by the position sensor device have positively been found to be faulty.
The invention provides a further operating method for a vehicle transmission in which predetermined shift positions, in particular at least one position of full engagement of a gear and/or at least one position in the selector track, are associated with profile depressions that are arranged on a movable element. The method includes the following steps:
a) Under predetermined conditions and in accordance with a predetermined characteristic, the transmission is actuated to seek a position that is associated with a profile depression.
b) A shake-down or vibratory movement is carried out to settle the first element (or another element coupled to the latter) into an essentially unbiased, force-free position, after detecting that the contact feeler element has substantially arrived at the depression. The shake-down movement is generated by applying an alternating pulsating force to at least one shifter element, so that the shifter element is at least once pushed quickly back and forth.
The invention provides a further method of detecting a change in position, or detecting a position relative to a reference point in a transmission. This further method includes the step of emulating at least one actuator device by means of a model that is incorporated in the control device. This method, too, applies to a transmission that has different rotary transfer ratios between an input- and output shaft corresponding to the different shift positions.
Shifting the transmission into one of the positions requires a movement in the shift direction and in some cases also in the selector direction. The movement in the selector direction is controlled by a first electrically controlled actuator device, and the movement in the shift direction is controlled by a second electrically controlled actuator device. The first and/or second actuator device is equipped with a displacement sensor device, and the transmission has at least one electric control device to control the actuator devices.
According to a proposed embodiment of the invention, the actuator device for the selector movement and/or shift movement is emulated in the control device, e.g., through a model of a servo-control loop.
According to a preferred embodiment of the aforementioned method, the command signal by which a position-control unit directs the movements of an actuating device is used also as input for the servo model that emulates the actuator device. As an example, the command signal can be an analog voltage signal.
The output signal delivered by the emulator model is preferably an equivalent counterpart to the signal of the displacement sensor device. The displacement sensor can be realized, e.g., by an incremental position sensor, in which case the output signal of the emulation model is preferably made available in terms of angular increments or in radian units.
It is particularly advantageous if the emulation model of an actuator device is based on characteristic variables or design data and/or at least one measured quantity of the actuator device. If the latter consists of a rotary drive mechanism, the characteristic variables can consist in particular of an rpm rate and/or a rotary acceleration, or of variables from which a rotary speed or acceleration can be calculated. If an electric motor such as a DC motor is used as a drive source, the characteristic design data used in the emulator model can, e.g., consist of the moment of inertia of the rotor, the electrical resistance of the rotor, and/or a torque constant. For a measured quantity, it is advantageous to use an rpm-dependent friction of the motor.
The use of an emulator model of the actuator device represents a particularly advantageous means for detecting a failure and/or malfunction of the displacement sensor. In practice, the fault recognition is based on calculating and evaluating the difference between the respective output signals of the displacement sensor device and the emulator model. A fault is indicated if the difference exceeds a given threshold. It is practical to set the sensitivity of the fault recognition through an appropriate selection of the threshold value, preferably taking the accuracy of the emulator model and possibly other factors into account. In one advantageous embodiment, an on/off hysteresis is used for an indicator flag signaling a fault or malfunction.
If a failure and/or malfunction has been recognized, appropriate measures are taken such as, e.g., initiating a special strategy for operating faults and/or making an entry into a fault memory.
In regard to a special strategy for operating faults, reference is hereby made to the German Patent Application Publication DE 199 00 820, the content of which is expressly incorporated by reference in the present patent application.
According to a further concept of the invention, an adaptation of the model is advantageously performed at a time when the displacement sensor device is fully functional. In case there is a difference between the output signals of the emulator model and the displacement sensor, the emulator model is adjusted to produce an output that more closely matches the signal of the displacement sensor.
The invention provides a further embodiment of a method which is particularly advantageous for controlling a transmission without the displacement sensor device that is part of the preceding embodiment. In this case, the displacement and/or position relative to a fixed point of the transmission is determined by the emulator model alone.
The scope of the invention also includes control devices that are equipped with a signal-evaluating capability and are operable to perform any of the methods of the foregoing description. Specifically, such control devices electrically control an actuator device that applies an actuating force to a first and/or second shifter element of a transmission, where the first shifter element is movable in a selecting/shifting track arrangement and where the position of at least one of the shifter elements can be detected by a position sensor.
Further included under the scope of the invention are transmissions of the type described above with at least a first shifter element that is movable in selecting/shifting track arrangement, and at least one second shifter element, an electrically controlled actuating device for at least one of the shifter elements, at least one control device for the actuator device, at least one position sensor device to determine the shift position of the transmission at any given time and, in addition, a redundant sensor device performing in certain predetermined situations a redundant determination of the shift position relative to the selector direction.
The invention further includes any transmission capable of performing one or more of the inventive methods described herein.
As a linguistic formality, where the names of features are connected by the word xe2x80x9corxe2x80x9d, this should be understood in the broadest sense, i.e., either as a logic type of xe2x80x9corxe2x80x9d (one or the other or both) or an exclusive xe2x80x9corxe2x80x9d (one or the other but not both), whichever fits the context.
The terms xe2x80x9ccontrolxe2x80x9d and xe2x80x9cregulationxe2x80x9d and their derivatives are used herein with a broad range of meanings encompassing closed-loop as well as open-loop control of devices, functions and processes, including in particular the DIN (Deutsche Industrie-Norm) definitions for regulation and/or control).
The novel features that are considered as characteristic of the invention are set forth in particular in the appended claims. The inventive method itself, however, both as to its mode of operation and its application in a motor vehicle, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.